Linear accelerators

Linear accelerators
Linear accelerators are accelerators which are able to accelerate charged particles. The size depends on the use of the accelerator as they can do lots of tasks. They can be used to inject charged particles into a sychrotron such as the large hadron collider. Smaller ones can be used in x-ray machines to supply electrons for medical use, linear accelerators also used for nuclear research these would be much longer. They can accelerate electrons protons or ions.

How they work
Charged particles will be produced at the start of the accelerator by a Van de Graaff generator. This beam of protons, electrons or ions will pass through hollow metallic cylinders called drift tubes. These tubes are connected to an alternating current and will have the polarity of there electric field altered at a specific frequency in such a way so that as the particles that move along the length of the tube are always being accelerated between gaps towards the next drift tube, they are always being attracted to the tube in front which will in respect to the tube behind have the opposite polarity of the charged particles. Acceleration of the charged particles only takes between the gaps of the differant drift tubes.

Length
The length of the tubes must increase to allow the frequency they are alternated at to stay the same, as when the charged particles are going faster they will cover more distance before the polarity of the next drift tube is switched relative to the last one. This enabled the frequency of switches to stay the same. In research the beams can be made to collide with a target and the results looked at.